Added to subnetwork class

- added theano_tick function
- added comments
Integrator example for #24 runs
Added templates folder and basal_ganglia

- Working towards getting bg example for #24
- stripped down the nengo bg template, made one function that both
  generates the bg and adds it to a network with input/output
- it compiles, but throws a theano error saying optimization couldn't
  happen because of a local_sum_mul_by_scalar or something
- TODO: test and make it work